Salt-affected soils in Bulgaria Biser Hristov

University of Forestry and ISSAPP “N. Poushkarov”, Sofia, Bulgaria: (bisseru@gmail.com)

INTRODUCTIONSalt affected soils cover about 55 000 ha ofthe Bulgarian territory, 35 500 ha of whichhave been salted by natural processes and25 000 ha by industrial and drainageactivities before year 1990.This was the periodwith high industrialisation, irrigation andintensive agriculture (Teoharov et al. 2016).Salt affected soils in Bulgaria could be found inplaces such as, Danube river plain - thelowlands along the Danube river (Karaboazka,Svishtov-Belenska, Brashlenska, Tsibarska,etc.) and near some tributaries - Skat, Osam,Vit, Yantra, Studena, etc. In the UpperThracian Plain - around Plovdiv region, theTundzha plain - in the regions of Yambol, NovaZagora, Kermen, Radnevo, Karnobat, Straldzha(former Straldzha marsh), the Southern BlackSea coast - near the Burgas lakes - Vaya,Mandra and Atanasovsko lake. There are alsosome small spots of in western Bulgaria, closeto the rivers. (Teoharov et al., 2019).Nowadays the area of salt affected soils isslowly decreasing, due to using differentchemical amendments, lack of irrigation andbetter industrial technologies or closedindustrial pollutants.

METHODOLOGYThe monitoring of the soil salinization processis carried out in selected areas defined by theBulgarian Executive Environment Agency(ExEA). Eight soil indicators are measured(water-soluble Na+, Cl-, SO42-, HCO3- andCO32, exchangeable Na+, and CEC) andgroundwater properties. The spots arerepresentative of saline soils. The research onsalt affected soil in Bulgaria also are carried outby soil scientists form scientific institutes anduniversities.

DISCUSSION In last decade, the trends are maintained, insome of the areas there is a decrease in thecontent of exchanged sodium and a decrease inthe soil reaction (pH). The salinizationprocesses is determined by climate change,irrigation and intensive agriculture. Most of thesalt affected soils are mainly abandonedagricultural areas or wet areas with lowfertility. Their inclusion in the arable fund ofthe country is possible after correction of theexisting drainage systems and implementationof chemical amendments, in accordance withthe specific conditions of each site.By 1990 in Bulgaria were irrigated about 1,2million ha of agricultural land, in 2012 the areais only 541800 ha and sometimes much lower(Patamanska, 2012). A limited area withirrigation decreases the process of salinization.According to ExEA (2018) the salinization havehigh degrees in Plovdiv region and Varnaregion . The last one is influenced by theprocess of secondary salinization of industrialtype. The soils are located mainly around thesalt mine along the Provadia-Devnya saltpipeline and in the lower part of theProvadiyska River to its delta.

RESULTSThe process of natural soil salinization itsdevelopment is associated primarily with highgroundwater table with conditions for naturaldrainage, with periodic summer droughts inmost of the plains in Bulgaria, with thecharacteristics of local relief and some othernatural factors. Soil salinization is a process inwhich the content of water-soluble salts and /or exchanged sodium in soils increases inquantities that negatively affect theirproperties, respectively their productivepotential.Usually in Bulgaria the salinization is low, butthe soil dries out significantly in the summerperiod and salts are observed. In other places,spring rains brings shallow layer of water, butin summer the high groundwater carries up alot of dissolved salts, which "bloom" on thesurface.According to ExEA, in Bulgaria, about 35 500ha of arable land are affected by thesalinization processes, This is under 0.5 % ofterritory of the state. About 252 ha of the areahave soidc salinization. The processes mainlyaffect the districts of Burgas, Varna, VelikoTarnovo, Pleven, Plovdiv, Sliven, Stara Zagoraand Yambol (ExEA, 2018).The type and degree of salinization of the soil isdue to differences in the nature of salinization.The accepted classification divides into twoclasses of Solonchaks and Solonetz.In some salt afected areas high content ofwater-soluble salts, the Solonetz evolved asSolonchaks-Solonets. These are the mostcommon cases in Bulgaria. During the wetperiods the salts are washed and soils have theproperties of Solonetz. During the dry seasonscapillary salt water rise and soils have theproperty of Solonchaks (Teoharov et al., 2019).

REFERENCES

1.Executive Environment Agency (ExEA), 2018, Soil Salinizationreport. [online].http://www.eea.government.bg/bg/soer/2018/land-use/sastoyanie-na-pochvite2.Patamanska G., 2012. Changing existing irrigation systems andmanagement in Bulgaria for sustainable use of water, WaterManagement, 5-6, 29-35.3.Teoharov, M., Hristov, B. 2017. Soil, Earth and People - OurCare and Responsibility. Bulgarian Journal of Soil Science, 2(2),89–98. https://doi.org/10.5281/zenodo.25856744.Teoharov M. ed. 2019. Genetic and applied classifications ofsoils and lands in Bulgaria. BSSS pub. 214 p. ISBN 978-619-90414-3-7.

CONCLUSIONSThe degree of salinization processes in Bulgariais determined by different natural andanthropological factors such as precipitation,vegetation, land use, irrigation, drainagesystem, industrial pollution, etc. Conductedsoil researches and soil monitoring in our stateshow improvement of soil quality. In someobserved spots there are decrease in thecontent of exchangeable sodium and a decreasein the soil reaction also. Limited irrigation inlast decades also decreased the salinity levels.In some areas implementation of chemicalamendments were also used to decrease highconsecrations of exchangeable sodium.Nevertheless in low relief forms salinizationarising from rise of water table in soils withhigh the presence of sodium substances. Inpresent days there are also preserved saltaffected areas, because of protected halophytespecies and wet zones.

Fig 1. Salt affected soils in Bulgaria - Source ExEAhttp://eea.government.bg/eea/bg/publicat/2004-3/quality/soil/soil4.htm

Fig 2. Solonchak – Solonetz soils in vilage of Belozem – dis. Plovdiv, Bulgaria